From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2AE6C433EF for ; Fri, 11 Mar 2022 09:24:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237418AbiCKJZK (ORCPT ); Fri, 11 Mar 2022 04:25:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347482AbiCKJY5 (ORCPT ); Fri, 11 Mar 2022 04:24:57 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EFFDECC63 for ; Fri, 11 Mar 2022 01:23:48 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id BB322218FB; Fri, 11 Mar 2022 09:23:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1646990626; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AAebBo2Ox/zCWG7q1Ozd2d4et9J9l1aqgs2UCakv6jo=; b=ooLRvzEnI4KmFKpBb9Pc+ki9faKRUrGslNUu+7nyxD19DSn5pgr189oGyTZz5oFFrlH6D4 +TtkDOGMRtLBfcBc7wOhxWtdhS6uiCI3gF6yDcPTSH25fFKt3EO7tYUYsaTg3ly7U1etB+ 22xzAPqL0K84d/GWooPfI4GG8x6DH18= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1646990626; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AAebBo2Ox/zCWG7q1Ozd2d4et9J9l1aqgs2UCakv6jo=; b=ZTgzHVxnl1QG3AfrwIvrsL7F43IP0UancSHTbVFeKXYRTqqkqKjysVUu4LNi5COkDsbFTj A2ja3YO/jD0yWtCw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 45B1913A82; Fri, 11 Mar 2022 09:23:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id K14HDiIVK2KPVAAAMHmgww (envelope-from ); Fri, 11 Mar 2022 09:23:46 +0000 Date: Fri, 11 Mar 2022 10:23:44 +0100 From: Oscar Salvador To: Andrew Morton Cc: Dave Hansen , "Huang, Ying" , Abhishek Goel , Baolin Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N_CPU state Message-ID: References: <20220310120749.23077-1-osalvador@suse.de> <20220310183951.cb713c6ae926ea6ea8489a71@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220310183951.cb713c6ae926ea6ea8489a71@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 10, 2022 at 06:39:51PM -0800, Andrew Morton wrote: > What I'm not getting here (as so often happens) is a sense of how badly > this affects our users. Does anyone actually hotplug frequently enough > to care? Well, I would not say it is critical, it just regresses the time hotplug operations take. How bad is that? I guess it depends. Memory hotplug operations are already slow per se, so I would say expectations are not that high. But it speeds up the process, that is for sure. e.g: In a system with 144 CPUs and 2 Numa-nodes, set_migration_target_nodes() gets called exactly 144 times at boot time(one per every time a CPU is brought up), where only 2 calls would suffice, so you can get an idea. > If "yes" then I'm inclined to merge this up for 5.18 with a cc:stable. > Not for 5.17 because it's late and things are looking rather creaky > already. > > And I'll add a > > Fixes: 884a6e5d1f93b ("mm/migrate: update node demotion order on hotplug events") > > which is that patch's fourth such bouquet. Thanks Andrew! -- Oscar Salvador SUSE Labs